Art of drawing sheet metal



0. MAY

' ART OF DRAWING SHEET METAL Filed April 21, 1926 1% W ll? 1 fiz AINVENTOR A ATTORNEY ments to provi PATENT OFFICE.

one MAY, or NEWARK, NEW JERSEY.'

ART OF DRAWING SHEET METAL.

Application April 21, 1926. Serial No. 103,453.

This invention relates to the art of drawing sheet metal and similarmaterials, and has for its primary object to provide an improved methodfor drawing a sheet metal blank in the form of a relatively shallow onof large diameter into a relatively deep she I of greatly reduceddiameter in a single operation.

It is well known v.that in the drawing of sheet metal there is adefinite limit to the possibility of reducing a blank of one diameter toa smaller diameter, or where the shell has already been drawn inreducing the same to a smaller diameter in one operation. Suchlimitation in the diameter reduction which is possible in a singledrawing tion so that upon reaching the permissible limit or surpassingthe same, the metal is subjected to a tearing strain by the transmissionthereto of the pressure forces of the punch. Therefore, in order toobtain the greatest efliciency, it becomes necessary to first efiect thereorganization of the crystal line structure of the metal by subjectingit to a proper heat treatment so that the metal structure will becapable of withstanding the high strains or stresses, and secondly, toreduce the surface friction created in the drawing operation as much aspossible.

It is the pufipose of my present improvemetal blank may be drawn in asingle operation to a comparatively small diameter without firstnecessitating such a heat treatment thereof, and with practically theentire elimination of the frictional tearing strains incident to theprior art methods, to the end that a perfectly drawn shell ofcomparatively sma 1 diameter may be produced without the slightestindication of shrinking.

Essentially, my improved method comprehends subjecting the sheet metalblank to pressure between male and female draw ing dies without the useof a pressure plate and wherein the metal sheet is drawn over therounded edge of the hollow annular female die, and during the drawingoperation relieving the metal sheet from frictional e a methodwherebythesheet bearing contact upon the edge of" the female one simple andpractical embodiment of the invention, and in which similar referencecharacters designate corresponding parts throughout the several views,-

Figure 1 is a more or less diagrammatic sectional view through a part ofthe apparatusshowing the blank sheet metal form arimprored ranged inposition upon the female drawing I die at the start of the drawingoperation; Fig. 2 is'a similar view showing an intermediate stage of thedrawing operation, and

Fig. 3 is a like view showing the relative positions of the parts afterthe drawing operation has been completed and the blank converted into arelatively deep cylindrical shell of small diameter.

In the drawing of tubular or cylindrical sheet metal forms, it ispossible to almost entirely eliminate surface friction by employing theold prior art method, commonly referred to as the inside out method. Inother Words, starting with a large diameter shallow cup-shaped blank,said blank is repeatedly drawn in reverse directions until it is finallyreduced to the desired depth and diameter. Such a method is disclosedfor instance, in the U. S. patent to Hodge No. 460,550, of October-6,1891. In the use of this method however, in each drawing operation,there is a very small reduction "ofdiameter, in order that wrinkling ofthe metal may be avoided. The method however, has the advantage that thestresses to which the metal is subjected are comparable to those whichoccur in the ordinary metal rolling process, and the material is notsubjected to the severe strains or stresses which occur in the usualdrawing operation by bending the metal over or upon relatively sharpcorners. If it is attempted to draw the metal to final shape in oneoperation by rounding such sharp corners or increasing their radius; it

becomes necessary to subject the metal toa which the metal is subjected.Y Y

By means of my invention,'I propose to draw the sheet metal cup shapedmember to its final shape in one operation, thereby expediting thequantity production of such drawn articles over that possible in the useof the prior art process above referred to and at the same time obtain aperfectly drawn product.

To the above end, I have illustrated in the accompanying drawing atypical example of apparatus, for the purpose of elucidating thedescription of my new method, wherein center punch 6 and the ring orsleeve 8 with respect to each other and with relation to the femaledrawing die 5.

In the operation of my improved method, the sheet metal blank indicatedat 10 which has previously been stamped between suitable dies intoshallow cup-shaped form of relatively large diameter is placed in aninverted position upon the upper rounded edge 7 of the female die 5, theannular wall of the blank extending downwardly upon the outer face ofsaid drawing die. The center punch 6 is now moved downwardly underpressure to force the center of the blank into the bore of the femaledie member 5 and simultaneously the sleeve 8 is moved upwardly so thatthe shoulder 9 thereof engaging the lower edge of the flange 11 of theblank will exert an upward lifting force thereon, thus relieving themetal sheet as it is drawn over the convex end surface 7 of the femaledie of frictional res sure upon said surface. In this operationtherefore,

, practically the only frictional pressure on the sheet metal whichoccurs, takes place between the opposite surfaces of the sheet metal andthe side face of the male die member 6 adjacent its lower end and theinner surface of the female die 5 adjacent the juncture thereof with therounded edge 7 of said die, or substantially at the point indicated at12 in the drawing. This compressing pressure upon the sheet metal as it1s forced into the hollow tubular female d1e 1s advantageous as itproduces an ironing action which effectually eliminates any semblance ofwrinkles in the metal sheet which might occur as it isdrawn downwardlyinto the female die member. This downward movement of the center punch 6and the up- Wardmovement of the sleeve or ring 8 continues until thedrawing operation is completed so that at no time during said opera-.tion will there be any severe frictional contact of the metal sheetupon the upper rounded edge of the female die member 5. Therefore, inthis single drawing operation, the large diameter metal cup is convertedinto the comparatively small diameter deep metal shell entirely freefrom wrinkles or other imperfections, as shown in Fig. 3 of thedrawings.

From the foregoing description considered in connection with theaccompanying drawing, my new method of drawing sheet metal in itsseveral essential particulars, will be clearly understood. It will beseen that in so far as the perfection of the final product is concerned,I secure as good or better results as the old inside out method of theprior art, but with the elimination of the intermediate drawingoperations. Therefore, by means of my improvement,'it will j be evidentthat quantity production of-such articles can be greatly expedited andwith a material decrease in expense incident to the elimination of muchof the apparatus heretofore required. It will, of course be understoodthat the apparatus illustrated in the accompanying drawing is merelysuggestive, and that the essential step of relieving the metal sheet offrictional strains in the drawing operation might be carried out invarious other ways. Accbrdinglyyit is to be un derstood that I reservethe privilege of resorting to all such legitimate modifications andadopting other alternative forms of apparatus for carrying out themethod as may be fairly considered within the spirit and scope of theinvention as claimed.

I claim:

1. The method of drawing a blank of sheet material into a cylindricalshape which consists in drawing the sheet under pressure over one endedge of a female drawing die and simultaneously applying a pressure tothe sheet in a direction 0 posite the drawing pressure exteriorly ofthat portion of the sheet subjected to the drawing pressure to relievethe sheet from positive frictional contact with the end of the die.

2. The method of drawing a blank of sheet material into a cylindricalshape which consists in drawing the sheet under pressure into a femaledrawing die over a convex end edge thereof, and simultaneously appl inga positive lifting force to the outer edge of the sheet to relieve thesame of positive fric tional contact with said convex end of the femaledrawing die. 1

3. The method of drawing'metal sheets into cylindrical shapes whichconsists in first arranging a shallow cup-shaed sheet metal blankuponthe rounded en edge of a female drawing die, and then subjecting theblank'to the action of a center punch to force the sameunder pressureinto the female die and simultaneously with the movemerit of thecenterpunch and continuously during the drawing operation, applying a force torelieve the metal sheet from positive frictional contact upon saidrounded edge of the female die. y

4. The method of drawing metal sheets into cylindrical shapes whichconsists in first arranging a shallow cup-shaped sheet metal blank uponthe'rounded end edge of a female drawing die, and then subjecting theblank to the action of-a center punch to force the same under pressureinto the female die, and applying an upward lifting force to the edge ofthe sheet metal plate continuously during the drawing operation tothereby sustain said sheet metal plate out of positive bearingfrictional contact upon the end edge of the female drawing die.

5. In a sheet metal drawing apparatus, relatively movable male andfemale die members, said female die member having a convex edge overwhich the metal sheet is 'drawn, and means "to exert continuous unbrokenpressure on the metal sheet eiteriorly and in a direction opposite themovement of the male die member for relieving frictional bearingpressure of the metal sheet upon said edge of the female die memberduring the drawing operation.

6. In a sheet metaldrawing apparatus,

male and female die members, one movable relative to the other, saidfemale die member having a convex edge over which the metal sheet. isdrawn, and continuous un- 'the metal sheet upon saidedge of the femaledie member during the drawlng operation;

7. 'A method of drawing a sheet metal cup shaped member into a member.of similar shape of less diameter and greater length,-

consisting in drawing the same under pressure into a female die over theedge thereof and simultaneously applying a'positive lifting force to theedge of the cup shaped member to relieve the same of positive frictionalcontact with the edgeof the female die.

8. 'lhemethod of drawing the sheet metal cup shaped member into a memberof simi lar shape of a less diameter and greater length consisting indrawing a member under pressure in a reversed position into a drawingdie over the edge thereof and simultaneously applying a positive liftingforce to the outer edge of the cup shaped member to relieve the same ofpositlve frictional contact with the end of the female die.

In testimony that I claim the foregoing as my invention, I have-signedmy name hereto;

j o'r'ro MAY.

